秦岭落叶松及油松凋落物可溶性有机碳含量及其紫外-可见光谱特征

森林凋落物分解过程中可溶性有机碳含量的变化对研究森林凋落物在生态养分循环中凋落物分解快慢及其养分释放机制有着重要的作用。通过秦岭太白县境内落叶松林、油松林不同分解阶段(L-F-H)凋落物室内10d恒温(25℃)浸提实验,初步分析了凋落物分解过程中可溶性有机碳(DOC)含量分布特征及其紫外-可见光谱特征。实验结果表明:凋落物DOC含量L层F层H层;DOC_(油松林)DOC_(落叶松);浸提液紫外-可见光谱自200nm到800nm吸光度值趋于减小,L层、F层浸提液谱线呈现明显的单波峰,H层谱线存在端吸收,各谱线的波峰或端吸收都出现在200nm附近;肩峰出现在240～280nm范围内,推测样品中有芳香环结构存在。凋落物不同分解阶段浸提液DOC含量与200nm处吸光度值呈现较强相关性(R~20.9)。     

用分光光度法测定有机质的研究

在强酸性溶液中、165℃和催化剂作用的条件下,土壤中的有机碳被K2Cr2O7迅速氧化,而K2Cr2O7中的Cr6+还原成Cr3+,Cr3+在600nm波长上有特征吸收,其吸光度与有机碳的浓度成正比。根据吸光度可计算出土壤有机质的含量。实验证明试剂和工作曲线的斜率有很好的稳定性和重现性。分光光度法测定有机质快速、准确。     

水中二氧化氯静态膜分离的研究

利用二氧化氯在360nm处有一最大吸收峰以及二氧化氯能够通过微孔性聚四氟乙烯膜的特性进行了静态膜分离的研究。通过研究温度和二氧化氯的浓度对分离效果的影响,可以确定：温度越高越有利于二氧化氯的膜分离,但温度高于20℃时二氧化氯会发生分解,故最佳分离温度应为20℃。     

双波长K系数方程法同时测定水样中的砷和磷酸盐

双波长K系数方程法同时测定水样中的砷和磷酸盐，是指选定两个测定波长λ1、λ2，将磷酸盐、砷在λ2处的吸光度转化为λ1处的吸光度，列出一个二元一次方程组，解得磷酸盐、砷在λ1处的吸光度，进而求得水样中的磷酸盐、砷含量。     

用变色酸法测定废水中的甲醇

目前西南油气田一些监测站尚不具备用甲醇分析气相色谱法的相应能力,因此通过比色定量分析实验,用变色酸法测定废水中甲醇。研究结果表明:标准溶液在570 nm处吸光度最大;对甲醇含量为8 μg/mL的标准溶液,显色剂最佳用量为0.5 mL。按照实验方法配制标准系列,测定、统计、回归出甲醇标准曲线。该方法对甲醇的最低检出浓度为0.080 mg/L。加标回收结果表明,该方法的准确度和精密度均较好,由此确定了用变色酸法测定废水中甲醇的最佳反应条件。     

页岩气压裂返排液破胶剂筛选

页岩气压裂返排液在进行深度处理前需要破胶预处理。实验选用次氯酸钠(NaClO)、过氧化氢(H_2O_2)、聚合氯化铝(PAC)三种药剂作为破胶剂。研究表明,NaClO在投加量为5g/L,pH值为7,搅拌时间为20min的最优条件下,压裂返排液COD_(Cr)、浊度、SS、黏度、多糖浓度均下降;以浊度和多糖为评价指标时,浊度下降88.6%,多糖浓度下降85.4%,取得了很好的破胶效果。页岩气压裂返排液破胶剂筛选研究,为后续有效处理返排液提供了必要的条件。     

船舶压载舱中环境因子对夜光藻生长的影响研究

采用正交实验法分别从气液接触面积与液体体积比、温度和初始浓度3个影响因子4个水平对夜光藻的生长变化率进行研究。研究结果表明,在实验范围内,气液接触面积与液体体积比为0、温度为17℃、初始浓度为10×106cell/L时,藻细胞浓度递减速率最大;影响夜光藻细胞浓度变化速率因素的强弱顺序是：初始浓度〉气液接触面与体积比〉温度。     

紫尿酸铵比色法测定大气降水中的钙

在碱性溶液(pH10.4—11.1)中,钙离子与紫尿酸铵生成橙红色的稳定络合物,在500nm处有最大吸收,钙浓度在2.5—25μg/50ml范围内符合比尔定律,表观摩尔吸光系数为1.2×10~4L·mol~(-1)·cm~(-1),桑德尔灵敏度为0.003μg/cm~2。本法快速、准确、可靠,回收率为94—104％。     

BHTTT试剂的合成与高灵敏,选择性的光度法测定痕量钴

应用乙二胺代替丙胺,巧妙地合成了 BHTTT 试剂,产率由48％提高到65％,截至目前为止,尚未见报道。研究了 Co(Ⅱ)-BHTTT—吐温-80显色配位体系的特性。在 pH5.0～9.5范围内,显色体系光谱吸收峰(λmax)为385nm,试剂空白λmax 为225nm,对比度(Δλ)较高,Δλ=160nm。摩尔吸光系数ε_(385)=2.35×10~5L.ml~(-1).cm~(-1).在低浓度吐温80和 DL-半胱胺酸盐酸盐存在下(具有相当高的选择性),Co(Ⅱ)与BHTTT 组成比为1∶2.在0.5～10ug/50ml 范围内,服从比尔定律.检出最低浓度0.005mg/L,测定上限为0.5mgCo/L.此方法已成功地应用到测定玫瑰花、当归根、人发、环境水样和钢铁中痕量钴.     

FS—IV^＋流动注射仪测定地表水中氨氮

铵与碱性酚和次氯酸钠反应生成靛蓝化合物,其色度与铵的浓度成正比,亚硝基氰化物使蓝色增强,在660nm处测量吸光度值;采用Flow Solution-IV^＋（FS-IV^＋）流动注射仪测定地表水中氨氮,检测范围0～10．00mg／L,检出限0．008mg／L,分析速率51个样S／h;对方法精密度、准确度、加标回收进行了实验,结果令人满意。该方法具有自动进样、分析速率快、试剂耗量低等优点,可应用于大批量常规地表水分析。     

温度、酸碱度和盐离子浓度对curcin紫外光谱和荧光光谱的影响

将麻疯树核糖体失活蛋白curcin在不同温度、酸碱度和Na Cl浓度下进行孵育,测定其紫外光谱和荧光光谱的变化,对影响其结构稳定性的因素进行初步探究。研究结果显示,curcin对温度和p H变化相对敏感。当温度上升到70℃后,紫外吸收明显增加,在348nm时新增一个明显的荧光激发峰。极端p H值对curcin结构影响同样较大,特别是当p H值为11时,在348nm处新增荧光激发峰。上述现象表明,温度和酸碱度的改变可能导致curcin中含色氨酸的疏水核心结构出现暴露在外的变性过程。Curcin对上述两个因素的敏感性提示其稳定性还有待提高,才能满足蛋白质药物开发的需求。     

Spectral properties of salt crusts formed on saline soils

Rapid identification and large-scale mapping of salt-affected lands will help improve salinity management in watersheds and ecosystems. This study was conducted to examine spectral reflectance of soils treated with saline solutions containing NaCl, NaHCO3, Na2SO4, and CaSO4.2H2O. Spectral reflectance was measured upon salt crusts formed on two soils (Torrifluvents) subirrigated with saline solutions of 500, 1000, and 1500 mmolc L-1 with a spectroradiometer in the visible and near-infrared region (400-2500 nm). Spectral analyses revealed that samples of gypsum crusts have diagnostic absorption features near 1023, 1225, 1457, 1757, 1800, and 2336 nm, whereas halite crusts have diagnostic absorption features near 1442, 1851, 1958, and 2226 nm. Several broad absorption features were seen in the spectra of the crusts of sodium bicarbonate at 1243, 1498, 1790, 1988, and 2356 nm. The spectrum of soils treated with sodium sulfate exhibited absorption features at 1243, 1472, 1677, 1774, 1851, 1968, and 2245 nm. Crystal size or salt concentrations did not affect the positions of the absorption bands of the salt crusts. However, reflectance increased as particle sizes decreased or with increasing presence of salt crusts. Spectroscopy can be used under certain conditions to identify the presence of primary diagnostic spectral features of gypsum, nahcolite, thenardite, and halite crusts.     

Landsat ETM+ Images in the Estimation of Seasonal Lake Water Quality in Boreal River Basins

We investigated the use of Landsat ETM+ images in the monitoring of turbidity, colored dissolved organic matter (CDOM), and Secchi disk transparency (Z(SD)) in lakes of two river basins located in southern Finland. The ETM+ images were acquired in May, June, and September 2002 and were corrected for atmospheric disturbance using the simplified method of atmospheric correction (SMAC) model. The in situ measurements consisted of water sampling in the largest lake of the region, routine monitoring results for the whole study area, and Z(SD) observations made by volunteers. The ranges of the water quality variables in the dataset were as follows: turbidity, 0.6-25 FNU; absorption coefficient of CDOM at 400 nm, 1.0-12.2 m(-1); Z(SD), 0.5-5.5 m; and chlorophyll a concentration, 2.4-80 mug L(-1). The estimation accuracies of the image-specific empirical algorithms expressed as relative errors were 23.0% for turbidity, 17.4% for CDOM, and 21.1% for Z(SD). If concurrent in situ measurements had not been used for algorithm training, the average error would have been about 37%. The atmospheric correction improved the estimation accuracy only slightly compared with the use of top-of-atmospheric reflectances. The accuracy of the water quality estimates without concurrent in situ measurements could have been improved if in-image atmospheric parameters had been available. The underwater reflectance simulations of the ETM+ channel wavelengths using water quality typical for Finnish lakes (data from 1113 lakes) indicated that region-specific algorithms may be needed in other parts of the country, particularly in the case of Z(SD). Despite the limitations in the spectral and radiometric resolutions, ETM+ imagery can be an effective aid, particularly in the monitoring and management of small lakes (<1 km(2)), which are often not included in routine monitoring programs.     

OPTICAL CHARACTERISTICS OF NEW ZEALAND RIVERS IN RELATION TO FLOW1

ABSTRACT: Six years (1989–1994) of data from New Zealand's National Rivers Water Quality Network were used to characterize the optical water quality regime of river waters as regards: visual clarity (black disc visibility), turbidity, and light-absorbing aquatic humic material (referred to as ‘yellow substance,’ measured as light absorption at 440 nm). Quantitative relationships between optical water quality variables and flow in rivers are well-described by power law expressions. Visual clarity usually decreases strongly with increasing flow in individual rivers. There is a strong, inverse relationship between turbidity and visibility, but, because of differences between sites, turbidity is not a good general predictor of visual clarity (the attribute of real interest) in rivers. Yellow substance tends to increase with increasing flow, probably because during rainstorms, soil water high in yellow-colored humic material, rather than rain water or ground water, dominates discharge. Therefore, rivers are typically clear and low in humic matter at low flow, and turbid and yellow-colored at high flow.     

EFFECT OF “WHITING” ON OPTICAL PROPERTIES AND TURBIDITY IN OWASCO LAKE,NEW YORK1

ABSTRACT: The effects “whiting” (CaCO₃ precipitate) had on the optical properties and turbidity of the epilimnion of Owasco Lake, New York, were studied during the summer of 1985. Turbidity was partitioned according to “whiting” and non-“whiting” components utilizing a simple acidification procedure. Diffuse light attenuation was partitioned according to the attenuating processes of absorption and scattering. “Whiting” was present most of the summer. Two major “whiting” events occurred that caused major increases in turbidity and the attenuation of light. “Whiting” was the principle regulator of turbidity during the study; it caused increases in light attenuation by increasing light scattering. “Whiting” events can easily be mistaken by the public for phytoplankton blooms.     

Predictive models of turbidity and water depth in the Doñana marshes using Landsat TM and ETM+ images

We have used Landsat-5 TM and Landsat-7 ETM+ images together with simultaneous ground-truth data at sample points in the Doñana marshes to predict water turbidity and depth from band reflectance using Generalized Additive Models. We have point samples for 12 different dates simultaneous with 7 Landsat-5 and 5 Landsat-7 overpasses. The best model for water turbidity in the marsh explained 38% of variance in ground-truth data and included as predictors band 3 (630–690 nm), band 5 (1550–1750 nm) and the ratio between bands 1 (450–520 nm) and 4 (760–900 nm). Water turbidity is easier to predict for water bodies like the Guadalquivir River and artificial ponds that are deep and not affected by bottom soil reflectance and aquatic vegetation. For the latter, a simple model using band 3 reflectance explains 78.6% of the variance. Water depth is easier to predict than turbidity. The best model for water depth in the marsh explains 78% of the variance and includes as predictors band 1, band 5, the ratio between band 2 (520–600 nm) and band 4, and bottom soil reflectance in band 4 in September, when the marsh is dry. The water turbidity and water depth models have been developed in order to reconstruct historical changes in Doñana wetlands during the last 30 years using the Landsat satellite images time series.     

Concentration‐Duration‐Frequency Curves for Stream Turbidity: Possibilities for Assessing Biological Impairment1

Abstract: Siltation and subsequent biological impairment is a national problem prompting state regulatory agencies to develop sediment total maximum daily loads (TMDL) for many streams. To support TMDL targets for reduced sediment yield in disturbed watersheds, a critical need exists for stream assessments to identify threshold concentrations of suspended sediment that impact aquatic biota. Because of the episodic nature of stream sediment transport, thresholds should not only be a function of sediment concentration, but also of duration and dose frequency. Water quality sondes can collect voluminous amounts of turbidity data, a surrogate for suspended sediment, at intervals that can be used to characterize concentration, duration, and frequency of elevated turbidity events. To characterize turbidity sonde data in an ecologically relevant manner, a methodology for concentration‐duration‐frequency (CDF) curves was developed using turbidity doses that relate to different levels of biological impairment. To illustrate this methodology, turbidity CDF curves were generated for two sites on Little Pigeon River in the Great Smoky Mountains National Park, Tennessee, using over 30,000 sonde data measurements per site for a one‐year period. Utilizing a Poisson arrival approach, turbidity spikes were analyzed stochastically by observing the frequency and duration of recorded events over a turbidity level that relates to a biological dose response. An exponential equation was used to fit duration and frequency of a specified turbidity level to generate concentric‐shaped CDF curves, where at specific turbidities longer durations occurred less frequently and conversely shorter durations occurred more frequently. The significance of the equation fit to the data was accomplished with a Kolmogorov‐Smirnov goodness‐of‐fit test. Our findings showed that the CDF curves derived by an exponential function performed reasonable well, with most curves significant at a 95% confidence level. These CDF curves were then used to demonstrate how they could be used to assess biological impairment, and identify future research needs for improved development of sediment TMDLs.     

PREDICTING THE SUMMER PEAK BIOMASS OF FOUR SPECIES OF BLUE-GREEN ALGAE (CYANOPHYTA/CYANOBACTERIA) IN SWEDISH LAKES1

ABSTRACT: Stepwise multiple regression analysis was used to develop models predicting the summer peak biomass of Aphanizomenon flos-aquae, Anabaena flos-aquae, Oscillatoria agardhii, and Microcystis aeruginosa in four Swedish lakes. These analyses suggest that while epilimnetic total phosphorus concentration is the principal predictor of their peak biomass, other factors such as station mean depth, water temperature, total nitrogen, and total CO₂ concentration are also important.